The objectives of the Environmental Mutagenesis Test Development Program are two-fold. The first is the development of an integrated program for the routine testing of large numbers of chemicals for mutagenicity. This includes such diverse factors as test-system validation, identification and development of new test methods, development of an increased understanding of mutagenesis and development of a strategy and an organizational structure for conducting a large-scale testing program and interpreting the results obtained. The second objective is implementation: to test large numbers of commercial and environmental chemicals each year for mutagenicity.